Willing to exchange twenty years of her life as a warrant officer aboard the Weyland-Yutani ore transport vessel Nostromo in exchange for millions of dollars, Ripley was the only surviving member of the crew.
Ellen Ripley committed 20 years to the Nostromo mission to move an incredibly massive quantity of mined ore back from a remote Weyland-Yutani mining facility. While largely in stasis for the length of the trip, the payday to her was worth losing 20 years of her life. She would receive millions of dollars for the trip, had she returned. She would eventually be the final survivor of the fated Nostromo. She was the lone survivor of a deadly alien encounter on-board the Nostromo as the only human survivor. Accompanied by the ship cat Jones, she would eject from the ship just in time to escape the self-destruct sequence she triggered in order to end the risk of the alien menace. She would end up in stasis floating through space for nearly nine decades.
She would later be awoken from stasis, apparently rescued by a salvage crew. Long presumed dead she would soon face charges for "destroying" the Nostromo, and wasting the valuable assets on board.
After firing Ripley they would later recruit her to return to the original planet and discover what happened to some missing colonists. With a platoon of space marines they discover a nest full of aliens. Escaping another alien encounter after combating with and destroying their queen, she once again escaped into stasis aboard a ship, this time with a surrogate daughter, Newt, and Jones the cat.
Her final long trip through stasis would last longer than ever and eventually she would awaken, crashed on a prison colony planet, to survive yet another alien encounter. This time she would be pregnant with the Alien queen's offspring, and unfortunately she would awaken to find her ward, Newt and Jones, the seemingly longest lived cat companion in human history. She would not survive this encounter, however. She would eventually sacrifice herself in order to contain the alien menace once and for all.
Scientists hundreds of years later would resurrect her and attempt to harvest the alien queen inside her. They would fail.
According the extended history from the original DVD edition of the Alien Quadrilogy, she was willing to exchange her motherhood of her young daughter in order to maintain an adult relationship with her free of work commitments. Or that's how it was supposed to work anyway. She would of course never meet up with her daughter ever again, and by the events of Aliens, that chance had passed entirely due to the amount of time that had passed. She would however, find out that her daughter lived a satisfying life and had a family. She would however die believing that her mom was a criminal.